1. Field of the Invention
This invention relates to a battery pack suitable for use with electronic equipment such as a portable telephone.
2. Description of the Related art
A battery pack comprising a secondary battery such as a lithium ion cell has conventionally been employed as a driving power source for electronic equipment such as a portable telephone. The battery pack comprises a secondary battery including an aluminum case and a power generating element enclosed in the aluminum case. Positive and negative terminals project from upper and lower sides of the secondary battery respectively. A nickel lead is connected to one of the terminals and extends along the aluminum case with an insulating tape interposed therebetween. The nickel lead extends to the side of the secondary battery from which the other terminal projects. The secondary battery is further enclosed in a plastic case together with a protection circuit board on which circuit elements are mounted.
Reductions in the size and weight of the battery pack have recently been demanded for the purpose of miniaturization and cost reduction of the electronic equipment such as a portable telephone. In the foregoing conventional structure, however, the secondary battery made by enclosing the power generating element in the aluminum case is further enclosed in the plastic case. Thus, a double enclosing structure employed for the secondary battery poses definite limits to the cost and weight reductions. Furthermore, the protection circuit board is enclosed with the secondary battery in the plastic case in the foregoing structure. The protection circuit board also poses limits to the cost and weight reductions.
Therefore, an object of the present invention is to provide a battery pack which can reduce the size and cost thereof.
The present invention provides a battery pack adapted to be connected to an external circuit, comprising a battery case in which a power generating element is enclosed, the battery case having at least one side, a cover covering the side of the battery case so that a component disposing space is defined between the battery case and the cover, a circuit element disposed in the component disposing space and connected to the power generating element, and a terminal disposed in the component disposing space and connected both to the power generating element and via the cover to the external circuit.
According to the foregoing battery pack, the terminal to be connected to the external circuit is disposed in the component disposing space defined by the cover. Accordingly, a nickel lead need not be caused to extend from one of two terminals to the side of the other terminal as described in the description of the related art. As a result, the sides of the battery pack need not be covered with the plastic case. Further, the circuit element required for connection to the external circuit is disposed in the component disposing space defined by the cover. Thus, since all the necessary electrical elements are located inside the cover, no plastic case covering the overall secondary battery is required.
In a preferred form, either one of the battery case and the cover has a locking protrusion located in the component disposing space, and the other has a locking receiver with which the locking protrusion is engaged so that the battery case and the cover are assembled together. In assembling the battery pack, the locking protrusion is engaged with the locking receiver. Consequently, the cover can easily be mounted to the battery case.
In a battery pack using no plastic case, a protection circuit etc. is considered to be fixed to a side of the secondary battery by low-pressure molding of a resin. In this case, however, the molten resin is brought into a direct contact with the secondary battery. As a result, there is a possibility that the secondary battery may be deteriorated since the secondary battery is heated. On the other hand, in the battery pack provided with the locking protrusion and the lock receiving portion, there is no possibility that heat is applied to the secondary battery during assembly of the battery pack. Consequently, deterioration of the secondary battery can be prevented.
The present invention also provides a battery pack adapted to be connected to an external circuit, comprising a battery case in which a power generating element is enclosed, the battery case having at least one side, and a circuit element mounted on the side of the battery case and having a plurality of terminals including at least one electrically connected to the power generating element. Since no protection circuit board is used in this structure, the size and cost of the battery pack can be reduced.
The circuit element preferably includes a functional portion and has a laminated structure in which the functional portion is interposed between a pair of the terminals, and the circuit element is preferably mounted on the side of the battery case so that a direction of lamination is generally perpendicular to the side of the battery case. In this construction, the terminal for connection to the external circuit does not confront the side of the battery case. Accordingly, since the terminal portion does not contact with the battery case, the terminal and the battery case can reliably be insulated from each other.